Even in temperate climes, irrigation, whether lawn sprinkling or crop irrigation, is practiced extensively, and in hot and arid climes, is absolutely essential.
At the same time, water is a scarce and, in some places, expensive, natural resource. It is highly desirable to irrigate only when the soil requires it, and to stop when the soil has reached the desired amount of wetness. In those areas in which temperatures reach heights that make overhead irrigation wasteful of water or injurious to plants or both, it is desirable that irrigation not be carried out until the temperature is low enough to avoid those problems.
One of the objects of this invention is to provide automatic control over existing hydraulic irrigation valves, whereby irrigation is begun when the soil has reached a predetermined dryness, and is stopped when the soil has reached a predetermined wetness.
Another object is to provide such a device that is simple to manufacture, easy to use, and requires no external electric power or manual operation, operating on the water pressure available in any event.
Still another object is to provide such a device with an override system that prevents its actuating the irrigation valve when the ambient temperature is too high.
Other objects will become apparent to those skilled in the art of the light of the following description and accompanying drawing.